The present invention relates to a method for spraying a rust-protecting agent on the interior surfaces of straight and curved cavities by means of spraying.
The object of the present invention is to obtain a method for total application of a rust-protecting agent in narrow cavities, straight as well as curved ones, whereby the nozzle through which the rust-protecting agent is sprayed, airless or aircontaining, shall reach as near as possible the surfaces which are to be treated.
A further object is simultaneously to clean and to drive away dirt by means of said spraying.
It has previously been known to use nozzles having an axially through-bore for spraying of rust-protecting agents. When such a nozzle has been used for spraying in an enclosed space, e.g. in a frame side member of a motor vehicle, it is usually mounted on a tube bent at an angle. The tube together with the nozzle is introduced into the space through an access hole bored into the enclosed space. In order to obtain an equal distribution of the rust-protecting agent on all the walls of the space the nozzle is turned around during the subsequent spraying. It has, however, turned out to be difficult to obtain a coating of all surfaces of the rust-protecting agent and simultaneously avoid excess spraying of certain surfaces. Moreover, spraying by this method takes a relatively long time. Another drawback is that under certain circumstances it may be difficult to introduce a curved tube into the space to be rust-protected.
Prior art also includes nozzles having a central inlet bore and an outlet channel connected perpendicular thereto. Nozzles of this type are common as outlets nozzles on aerosole packages, and are not used for spraying in closed spaces because they spray in only one direction. Moreover, such nozzles have not been constructed for spraying of liquids under the high pressures which are utilized in industrial rust protecting treatment, i.e. 5-15 MPa and in certain cases more.
It is also known to arrange a sector-spraying nozzle on a straight tube, which is introduced in a straight chamber, whereupon during withdrawal of the tube a rust-protecting agent may be applied.
These known methods, however, suffer from a number of drawbacks. For example, a great number of holes must be bored in a vehicle in order to reach all folds and pockets, and a hole must also be bored at each curve of a hollow space to assure application to all surfaces in the space. However, it is evident that too many holes reduce the mechanical strength of the detail in question. Likewise such holes raise the risk for rust action in the holes per se as these often are placed on exposed places.
Moreover, it takes a considerable amount of time to bore all these holes, and to apply a rust-protecting agent by means of a curved nozzle in each of these holes, which raises labor costs considerably. It also increases the consumption of rust-protecting agents, which raises material costs.